Purpose:
Cataract surgery has been shown to provide modest intraocular pressure (IOP)-lowering effects in eyes with or without glaucoma. However, IOP measurements in most of the previous studies had been obtained in the sitting position. We investigated the effect of phacoemulsification on IOP in different recumbent body postures including supine and lateral decubitus (LD) position.

Methods:
This prospective observational study included patients who had no glaucoma and had planned to undergo phacoemulsification and intraocular lens implantation in one eye. Before and 1 month after cataract surgery, IOP was measured in both eyes using Tonopen AVIA. We measured IOP in the sitting, supine and LD (with the operated eye placed on the lower side) position. IOP was measured 10 minutes after assuming each position in a randomized sequence.

Results:
Twenty-nine patients participated in this study. Postoperative IOP was lower than the preoperative IOP when measured by Goldmann applanation tonometry in sitting position (13.8±1.9 mmHg vs 12.6±2.1 mmHg, P=0.007). The postoperative IOP was lower than the preoperative IOP for supine and LD position. The average decrease in postoperative IOP from preoperative IOP of the operated eye was 0.6 mmHg, 1.7 mmHg, and 3.0 mmHg in the sitting, supine, and LD position, respectively (P<0.001, Friedman test). In the non-operated eye, IOP did not change significantly after surgery (All P>0.05).

Conclusions:
Cataract surgery lowered IOP in the sitting position as well as in the supine and lateral decubitus positions. Such postoperative IOP reductions were greater in the recumbent positions than in the sitting position.